The invention concerns a method for the creation of a data feedback channel in a common frequency network having multi-channel transmission with which the transmitted data are modulated to a plurality of carrier frequencies proximate to each other in frequency space and transmitted in frames separated by synchronization symbols. The invention also concerns a circuit array for carrying out the method and for the realization of a data feedback channel between a receiver having receiver components to a transmitter of a transmitter network in common frequency network operation.
There is a long-felt need for a data feedback channel for use in broadcasting to allow interactive selection of transmitted data from a large data supply or to be able to facilitate billing according to actual media consumption.
Known in the art from WO 94/01825 is a system for the calculation of fees for electronic services. The consumer has a device in which the charges due are compared to a credit amount and subtracted from same to facilitate use of the service. Towards this end, there is a connection between a central computer and the device at the user location.
This system has the disadvantage that two differing types of transmission are selected for bi-directional communication between the user and the central transmission location. In addition, it is not possible to effect interactive operation, since the system is only designed for fee calculation.
Known in the art from WO 92/10038 is a fee calculation system for cable TV with which, similar to WO 94/01825, a device is situated at the user location. This device has the following components: a receiver for a first transmission procedure, a decoder in order to decode the received data, a monitoring circuit to verify the access authorization of the user, a transmitter to transmit data to a central location using a second transmission procedure as well as a demultiplexer for separation of the forward and feedback channels.
This system has the disadvantage that the transmission requires cables and therefore cannot be utilized for mobile receivers. There is the additional disadvantage that two differing transmission procedures are utilized. No information is disclosed with regard to the transmission method itself.
A fee calculation system for a so-called "Value Added Service" is known in the art from EP 601 523 A1 with which an identifier which identifies the data type is added to each data set at a central location and transmitted to the user. The user has a device having individual identification codes and stores the transmitted identifiers. Transmission of a control code by the central location facilitates a request for desired information from the user to the central location which is transmitted along with the identification code.
Disadvantageously, this publication only discloses the fact that the identification code is to be transmitted to associate the transmitted data with a particular terminal. No information is given concerning the transmission protocol used.
Known in the art from EP 595354 A1 is a fee calculation system for broadcasting. This system has a computer located on the transmitter side which stores different types of data, a receiver which receives these data and a transmission format which includes an identifier for each type of data. The receiver thereby comprises circuits for data processing of each data type and a memory for storing the identifiers. The computer transmits conversion data for the calculation of fees in irregular time intervals which are stored in the receiver and utilized together with the identifier for the calculation of fees. Data is transferred by the receiver via a telephone line back to the computer located on the sender side. The receiver requires access authorization previously granted by the computer.
The disclosed fee calculation system has the disadvantage that use requires an additional telephone line for the data feedback channel. Even in the event that such a line is available, additional costs result. In addition, a telephone line has a very small transmission bandwidth so that the transmission capacity is low.
Known in the art from EP 488289 A2 is a cable-related bi-directional video transmission system. A video signal in a base band is mixed to a particular frequency position in the radio frequency range and transmitted along a cable to the receiver. The frequency position of the video signal to be transmitted is determined by a control unit following request by the receiver. The control unit controls the mixer in the transmitter and receiver to effect transmission of the video and request signals within a frequency region which is not in use.
This system has the disadvantage that transmission requires a cable so that it cannot be used by mobile receivers. In addition, there is no description of how to effect high precision synchronization of the mixer in an inexpensive and straightforward fashion.
The purpose of the present invention is to realize a data feedback channel between a mobile radio receiver and a most recently received transmitter, wherein the transmitter and the receiver operate in multi-channel transmission mode within a common frequency network.